NEW YORK (FORTUNE) - After the publication of "How to Beat the High Cost of Gasoline --Forever," Fortune and CNNMoney received hundreds of e-mails from readers.

Many scolded us for not explaining what they believe to be a fact -- that ethanol consumes far more energy than it produces. But the experts we spoke to don't buy into that argument. Most researchers who look at this closely believe that the "negative energy" crowd is using old science, that they're disregarding advances in technology and that the research tends to focus on corn ethanol, not cellulosic ethanol, which is the future of the industry.

More from Fortune 10 dumbest iPhone apps The surfin' CEO McDonald's wins with global palates FORTUNE 500 Current Issue Subscribe to Fortune

Beat the high cost of gasoline. Forever! Stop dreaming about hydrogen. Ethanol is the answer to the energy dilemma. It's clean and green and runs in today's cars. And in a generation, it could replace gas. (Full story) Biorefinery breakthrough No one has ever brewed biofuel from straw on a commercial scale. With Shell's backing, Iogen is likely to be the first. (Full story) Fill 'er up, Willie Mamas, don't let your babies grow up to be oilmen. Give 'em biodiesel! That's the refrain of the new troubadour of renewable fuels, Willie Nelson. (Full story) Virgin in the oil patch Richard Branson doesn't claim to be an energy guru. But he's bullish on ethanol. And once upon a time, he didn't know much about airlines or records or phones, either. (Full story)

A recent article in the journal Science looked at all these issues and concluded that ethanol is far less "petroleum-intensive" than gasoline. Find that article and far more research at the Web site of the University of California researchers who wrote the article.

The overwhelming nature of our correspondence from readers suggests, however, that this is a lively debate that goes far beyond the scientific talking points. We continue to welcome your views at this online forum. -- Adam Lashinsky, FORTUNE senior writer

------------------------

Gentlemen,

My congratulations to you and the magazine for stepping forward and identifying ethanol as our country's best hope. An outstanding job, but as a freelance editor on weekends and nights for a book on the subject, I'll weigh in with a couple of comments from the new book, "Alcohol Can Be a Gas! Fuelling a Revolution".

The mileage question is not accurate because of the lack of understanding on BTUs. Heating value has very little to do with a material's value as fuel -- it's simply the amount of energy theoretically given off if a material is burned with an optimum amount of oxygen. Studies claiming gasoline's superior mileage assume the two fuels burn with equal efficiency in your engine. Nothing could be further from the truth.

Very little of a fuel's energy becomes work (miles per gallon) in an internal combustion engine. Theoretically, 10 percent of fuel's energy goes into friction, 15-20 percent becomes work, and the remaining energy is waste heat and exhaust. In reality, many cars on the road only get 15 percent or less gasoline energy converted into work. Alcohol, on the other hand, has achieved 48 percent work efficiency in the lab, and 43+ percent efficiency on the road . Mileages as high as 22 percent above gasoline's have been recorded in studies with high compression engines

As per corrosion, I believe the final word on the safety of alcohol in fuel systems is to be found in the Automotive Service Excellence Manual published in 1996 entitled "Changes in Gasoline III." "Vehicle fuel tank and fuel system components from autos operated for extended period on these blends [of alcohol] were removed, cut open and examined. These tests have generally concluded that alcohol does not increase corrosion in normal, everyday operation."

"Sugar cane is the most energy-rich feedstock known to science." No. It's just something Brazil happens to have a lot of. Just like we grow corn. It is a FAR better feedstock than corn but huge amounts of ethanol per acre can be made from crops such as Jerusalem artichokes and sorghum. More USA friendly, so to speak.

Co-generation will be a key in providing new sources of energy from biofuels. What Brazil does with the electrical grid is just a start. The manufacture of ethanol produces carbon dioxide which can be used in many interesting ways. Check out ADM's integrated production site which allows them to farm tilapia!

For more information on jet fuel and ethanol, you should check out James Behnken on the web. Turbine engines can also fly on straight alcohol fuel.

The book addresses many of Mr. Wallace's concerns. Mr. Dimuro mistakes formaldehydes for acetaldehydes. Formaldehydes are only a problem with methanol. Thanks to substantial research and intelligent energy design, there need not be any input of pesticides, herbicides, or fertilizer in the process of making alcohol fuel so the oft-debated EROEI issue is a moot one. A change in agricultural practices is all that is needed for us to build what David Morris has called a carbohydrate economy.

It certainly is upsetting that farmers are taking such huge profits on E85 when they have a chance to show how their product is made on the cheap. Farmers should indeed learn the impact of public relations on such actions.

The subsidies to ethanol have resulted in a net increase in tax revenues, according to the GAO, because the money stayed home, rather than going to foreign countries and such. The amount of subsidies oil companies get dwarfs anything the farm lobby could dream up. Remove oil company subsidies, then we'll talk.

And tractors can run on ethanol, too. Straight ethanol.

Michael Winks

Brooklyn, NY

-----------

Typically I enjoy writing letters complimenting other journalists on their work. Sadly, I found your piece this morning on the future of ethanol in America lacking in one of the most fundamental aspects of reporting. That being hard facts to back up your article.

Ethanol does not burn cleaner than regular gasoline. For a reference you might try the court transcripts from American Petroleum Institute vs. EPA, heard by the Third Circuit Court of Appeals in 1995. It was the EPA's own attorneys who had to admit in that court case that the lower Reid Vapor Pressure involved in ethanol actually creates more smog. You will find the same information at the National Academies of Science.

As for fuel efficiency, if you will go to the government's own website, fueleconomy.gov and look up an Explorer with a V-6 engine, then compare that to the same Explorer under the Flexible Fuel category, you will find a 4-mile-per-gallon drop off in mileage if one uses E85 ethanol. Again, a function of the lower Reid Pressure associated with this fuel.

This morning in the journal Science, there is a well written piece on ethanol that cautiously predicts that ethanol can improve our energy situation, but only if technology improves for the planting, refining and distribution of the products. Even then, if you read their citations for that article, one will find loads of categories marked, "uncertain", "bad data" and so on.

As someone who has spent almost a year out on farms across America, only Science got the story right that plant yields for ethanol varies widely by county. Meaning one county consistently brings in 12 bushels an acre for corn, the next county over will produce 21 bushels an acre. Last year, one of the worst years for drought in the Midwest, saw a decrease across the board for crop yields.

I'm used to seeing articles like yours distributing by ethanol lobbying groups, but not in my copy of Fortune magazine.

Ed Wallace, Fort Worth Star Telegram, 570 KLIF AM Dallas

----------

I appreciated the recent article on ethanol as a substitute for America's dependence on middle-eastern petroleum. I agree that ethanol, like other renewable forms of energy, must take on a more commanding role if we are to ever break the addiction to oil as a form of primary energy.

I did get the impression, however, that you were presenting the ethanol argument from a fairly one-sided perspective. There are serious concerns with using ethanol as a primary fuel source, not least of which is the formaldehyde that is produced when it is combusted. Secondly, the matter of embodied energy, and net energy is much more than a "topic of endless Internet bickering", and deserves to be recognized as the actual scientific argument it is, and not belittled. There is concern that a large amount of natural-gas based fertilizers are consumed during the production of ethanol, which impacts the carbon-neutrality of ethanol greatly.

I agree that ethanol deserves more good press, as it is and will become a very important fuel source. With any subject, however, there are multiple viewing angles. Ethanol must be approached scientifically, while conscientiously considering all aspects. I do not believe it is as simple as encouraging the street to accept Ethanol as the next great investment. Creating sustainable energy sources is, unlike investing, not as simple as economics might suggest.

Respectfully, Johnathan DiMuro

Student, M.Phil in Engineering for Sustainable Development, Centre for Sustainable Development, Cambridge University

-----

In the early 80's, a family in town had an ethanol distillery in their back yard. My father told me that it would eventually replace gas. By the time I was old enough to own a car, ethanol was no longer available at the pump. I thought the concept was dead until I saw Ford advertising flex-fuel cars. I am glad to see this back in the news. Thank you for the well written article.

Rick

----------------

Just a quick note to congratulate you on the subject article. In fact, I lived in Brazil back in 1989 and you had the choice of gasoline or ethanol from sugar cane; back then you would have a car that would run on either one but not both, you could not switch. Throughout the past year I have been thinking why if almost 17 years ago the ethanol option was available in Brazil why can't it be now here in the US. At some point I thought that maybe it had a huge government subsidy in Brazil and it was not really sustainable but from your article I can see that it is very much alive.

To finish I was so stroke by Detroit not taking advantage to turn around the market with this opportunity, since '76 they have been trailing. First on emissions, then on efficiency, then on quality, then on design. This is their chance to get back on top of the game and they are just sitting on this?

Best, LFG

----------------------------

Adam: I have read that making ethanol and using to replace gasoline actually is inefficient and using more energy than just using gasoline. BTU for BTU, ethanol is a losing way to go. Just something to consider.

Robert

----------------

EROI = Energy Return On Energy Invested

In the Fortune article How To Beat The High Cost of Gasoline Forever, one little item was missing. That item is the energy cost of growing, processing and transporting the ethanol. How many barrels of oil are consumed making, transporting and using the herbicides, insecticides and fertilizers to grow this corn? How much oil is used irrigating the fields, fermenting and processing this "biofuel"?

Without the federal government subsidy would this biofuel be cost-effective? Without the federal government subsidy would Archer Daniels be in this business?

After all the energy-intensive steps from planting to gas station are considered, will this biofuel be a net producer or consumer of energy?

Edmund O'Shea, Arlington Heights, IL

--------------------------------

Adam: Found your piece on the net today. I support the idea and own a flex-fuel truck. But could you please do a follow-up as to why the HIGH COST OF ETHANOL? Living in Minnesota, I have found the price of ethanol not to be cost effective over gas. With the reduced mileage of the product, one needs to have over a .50 cents reduction to break even. If ethanol is cheaper to produce and only has 15 percent gas, there has to be A LOT OF PROFIT in someone's pocket.

Thank you, Tom Phenicie

-----------------

Your article on ethanol was thoroughly disappointing, as it ignored several important facts that make ethanol a very poor choice for the US economy:

-- The low corn prices you mention are only a result of extreme US subsidies given to corn farmers (powerful farm lobbies in Congress), and do not reflect the true market price of the substance. If ethanol's price was market-driven, it would not be economically feasible to use it as a gasoline substitute.

-- There is an incredible amount of energy consumed by the ethanol production process (including a fair amount of petroleum products - do you think that the farmers' tractors run on sunshine and smiles?) which makes the overall fuel production process less efficient.

-- By far the biggest problem is that ethanol/gasoline mixtures (such as E85) do not contain as much energy as 100 percent gasoline, so they make cars less fuel efficient. For example, check out the statistics from the EPA: http://www.fueleconomy.gov/feg/noframes/19264.shtml

-- Highway fuel economy goes from 21 MPG to 16 MPG when switching to ethanol, a decrease of almost 25 percent. Moreover, the fuel cost to drive 25 miles rose from $3.05 to $3.57, an increase of 17 percent. This is supposed to be better for the economy?

Perhaps methods of ethanol production from sources other than corn (which you spend only one paragraph describing) will offset these complaints. I don't have a miracle solution to US gasoline dependency, but I am sure that ethanol is not it (for the foreseeable future). I expect balanced reporting from a magazine such as Fortune...the bottom line is that your article blatantly omitted several key points regarding the feasibility of ethanol as a gasoline replacement, and anyone reading it would be ill-informed as to the true state of affairs.

Ted